1. Field of the Invention
The present invention relates to an elevator control apparatus, and more particularly to an elevator control apparatus which can reduce the number of signal lines connected between an operation management control device for controlling the operation management of an elevator car and a door control device for controlling the elevator door.
2. Description of the Related Art
A large number of highly reliable microcomputers and LSI circuits have been available at a low price in recent years. Microcomputers have been utilized for the sub systems of elevator control apparatuses.
A conventional elevator control apparatus illustrated in FIG. 1 has an operation management control device 11 installed in a machine room 10 and a door control device 21 installed in a car 20. The operation management control device 11 and the door control device 21 respectively comprise a microcomputer and the like, and are connected to each other through a number of parallel signal lines 30. The signal lines 30 include not only a number of signal lines 31 which transmit signals from the operation management control device 11 to the door control device 21, but also a number of signal lines 32 which in turn transmit signals from the door control device 21 to the operation management control device 11.
Connected to the door control device 21 is a door drive device 40 for driving the unillustrated door of the car 20 which includes a three-phase AC power supply 22, an electric power converting device 23, a motor 24 for the door, and a pulse generator 25 for detecting the number of revolutions of the motor 24. The electric power converting device 23 comprises an inverter which has a thyristor, a transistor or the like.
In the conventional elevator control apparatus as constructed above, the operation management control device 11 not only controls processing of calls from the car 20 and floors (not shown), but also controls the running, stopping, speed, etc. of the car 20. In addition, the operation management control device 11 also generates, in parallel, command signals commanding operations such as the opening and closing of the door of the car 20. These command signals are sent, in parallel, to the door control device 21 via the signal lines 31. The door control device 21 inputs the received command signals and generates, based upon these command signals, reference speed commands which command the rotation directions (directions in which the door opens and closes), and the number of revolutions, of the motor 24 for the door. The door control device 21 then generates torque commands based upon deviations between the reference speed command and the number of revolutions of the motor 24 for the door which is detected by the pulse generator 25, i.e., the actual speed, and further outputs these torque commands to the electric power converting device 23. The electric power converting device 23 controls the number of revolutions of the motor 24 for the door and thereby controls the door. The door control device 21 also generates and outputs status signals indicating the full opening and closing of the door, abnormalities in the opening or closing of the door, and so forth. These status signals are sent, in parallel, to the operation management control device 11 through the signal lines 32. The status signals include a detection signal from a mechanical contact sensor, or a photoelectric or supersonic wave non-contact sensor. Any one of the above sensors is attached to the edge of the door and generates a signal when a passenger touches or approaches the door while the door is closing. Upon receiving the detection signal from such a sensor, the operation management control device 11 switches to the door open command signal from the door close command signal in order to drive the door in the open direction.
There are, however, problems with the conventional elevator control apparatus in that because the operation management control device 11 and the door control device 21 are connected to each other through a large number of parallel signal lines 30, (i) the cost of the signal lines 30 becomes high; (ii) because of a large number of the signal lines 30, the installation of the elevator requires time and the maintenance time for the elevator becomes lengthy; and (iii) since all the signal lines 30 are connected in parallel, the operation management control device 11 and the door control device 21, each of which comprises a microcomputer, respectively require a large number of input/output process circuits, thereby resulting in complicated structures.